Actinobacillus pleuropneumoniae (A.pp.) is a causative agent of respiratory tract diseases and has led to high economic losses worldwide. Further research on the disease itself but also new prophylactic and therapeutic approaches are needed. Infrared thermography (IRT) of the thorax might offer a new selection method of high specificity to select swine with basic lung alterations for further diagnostics as a cheap and non-invasive method.
Clinical, computed tomographical (CT) and IRT examination were performed on 50 A.pp.-infected and 10 control pigs prior to infection, 4 and 21 days after infection. Clinical scores (ClS) were recorded daily and CT scores (CTS) were calculated. Both scores allowed the assessment of disease severities during the trial and were compared with IRT findings. IRT images were taken under controlled condition from both thorax sides after a 15 minutes cooling period. Absolute surface temperatures of the lung as well as temperature differences between lung and abdomen were compared between the three examination days. During necropsies at the end of the trial lung lesion scores (LLS) were determined.
On days 4 and 21 after infection, significant correlations were found between ClS, CTS and LLS and also on day 21 after infection between ClS and CTS. Influencing factors for the skin surface temperature of the thorax were ambient temperature, abdominal surface temperature and body temperature. On day 4 but not on day 21 after infection the right thoracal temperature was significantly higher and the difference between a thoracal region in the height of the left 10th vertebra and an abdominal region was significantly lower in infected pigs than in control pigs.
Results demonstrate that IRT can help to detect inflammatory lung alterations in the pig lung. The acute stage of infection can be better detected by temperature pattern in IRT than chronical stages. Ambient temperature plays is major interfering factor during the diagnostic of surface temperature. However, IRT examination does not give information about etiology of respiratory disease.
A Menzel, C Siewert, D Hoeltig, H Seifert, I Hennig-Pauka. Clinical diagnosis of lung diseases in pigs by infrared thermography. Proceedings of the 23rd IPVS Congress, 2014.